Robot-assisted techniques are today widely used in the medical sector, for example for intervention and diagnosis purposes.
Magnetic Resonance Imaging (MRI) and other various imaging techniques are also used for early diagnostic of cancers since MRI may help improving tumor perceptibility, while helping to target smaller tumor during biopsy.
Even if imaging techniques are well suited for detecting most of tumors, biopsies are generally still required for analyzing the malignancy of the tumor.
For example, a TransRectal UltraSound (TRUS) system may be used to perform a guided biopsy of the prostate in order to diagnose the malignancy of the tumor and its capacity to spread. TRUS images obtained with an ultrasound probe guide a physician inserting tiny radioactive seeds into the prostate during a transperinal brachytherapy. A perforated template is generally used to guide the physician during the insertion of the needle.
Unfortunately, TRUS offers limited contrast between tumors and healthy prostatic tissues, thereby inhibiting the identification of small tumors with diameter below 5 mm. This limits the efficiency of the biopsy, which is of great disadvantage. In fact, at least 20 percent of TRUS-guided prostate biopsy results in a false negative diagnosis, which implies that the cancer will go untreated, continue to evolve and spread if malignant.
Magnetic Resonance Imaging (MRI) systems may offer higher tumor perceptibility than standard TRUS procedures. However, MRI guidance implies to work in a specific environment. Indeed, typical clinical MRI systems generate magnetic fields ranging from 0.5 Tesla to 7 Tesla, hence no ferromagnetic objects can be introduced inside the MRI operating room since they would easily become dangerous projectiles. Moreover, MRI systems offer a very limited access to the patient, specially the closed-bore system.
Several MRI guided robots using MRI images have been proposed for breast, brain and prostate cancer treatments. For example, in the case of prostate treatment, a 6 Degree Of Freedom (DOF) robotic arm equipped with MRI compatible ultrasonic motors has been proposed for needle guidance procedures. However, they contain conducting materials creating Eddy currents which may interfere with the MRI magnetic field, thus generating image artifacts, which is of great disadvantage.
Pneumatic systems made with all-plastic components have also been proposed for offering optimal MRI compatibility. MRI compatible pneumatic step motors have been developed and integrated to a manipulator in order to move a 6 DOF robot. The proposed step motors use piezoelectric elements to control a compressed air flow, while the manipulator's position is measured by MRI compatible optical encoders. Many parts are involved in this complex design and step motors might skip steps and lose accuracy, which is of great disadvantage.
A different 6 DOF approach using linear pneumatic cylinders has also been proposed. In this system, the cylinders are actuated by pneumatic proportional pressure regulator valves controlled by piezoelectric elements. The pressure control system is located at the foot of the bed in order to limit non-linearity caused by air compressibility. To even reduce the non-linearity, special low friction cylinders may be used but it increases the cost of the system. Moreover, a complex control system should be used, which even increase the complexity and cost of the system.
It would therefore be desirable to provide an object manipulator that will reduce at least one of the above-mentioned drawbacks.